The present invention relates to a refrigerant recovery system and, more particularly, to a portable, electrically powered refrigerant recovery system which uses a single manifold to simplify manufacturing and assembly costs, a rectangular oil separator having internal baffles and being located between the manifold and a compressor, and a low-voltage control circuit which uses a latching circuit to avoid short cycling of the compressor and thereby increase compressor life. The present invention also relates to an improved push-pull recovery method in which superheated refrigerant vapor from the compressor is diverted directly to the manifold so that the vapor is returned to the unit being emptied to speed the recovery process.
Federal law now requires recovery of refrigerant from vapor-compression heat pumps, air conditioners and refrigerators to avoid perceived danger to the Earth's ozone layer. Refrigerant recovery machines are well known and are generally of the type shown schematically in FIG. 1 in which a compressor, and sometimes also a pump, is used to remove or recover the refrigerant from the system. The compressor in the direct vapor recovery system of FIG. 1 removes vapor from a system (not shown) in which oil has been separated from the vapor by passage through an oil separator/reservoir which receives the refrigerant vapor directly from the system being evacuated, and the compressed vapor is condensed prior to being stored in a tank (not shown) via the outlet connection.
A variety of refrigerant recovery systems, as well as refrigerant reclaiming processes, have been proposed as seen, for example, in U.S. Pat. Nos. 4,261,178; 4,363,222; 4,441,330; 4,539,817; 4,688,388; 4,766,733; 4,809,515; 4,809,520; 4,967,570; 4,998,416; 5,050,401; 5,072,593; 5,086,630; 5,090,211; 5,101,641; 5,176,008; 5,243,832; 5,291,743 and 5,357,768. Generally speaking, however, we have recognized that these various systems have disadvantages such as unduly complicated and costly manifold arrangements, the need for electrical heaters to vaporize incoming liquid refrigerant, impaired reliability due to the presence of control and back-up thermostats and sensitivity to intermittent opening and closing of safety switches resulting in shortened compressor life due to short cycling.
By way of example, U.S. Pat. No. 4,809,520 describes a portable recovery system which uses an input manifold which, in a manner similar to above-discussed FIG. 1, is connected to a combination heat exchange/oil-separation unit through a solenoid valve and has conventional valves and pressure gauges. The evaporator section of the unit is connected to the input of a compressor. The outlet of the compressor is connected to the condenser portion of the unit and, through a check valve and a pair of manual valves, to a refrigerant storage container. The evaporation portion of the heat exchange/oil-separation unit has a sloped internal baffle projecting downwardly from the top of the canister to force incoming refrigerant outwardly beneath the canister top. Likewise, the unit outlet has a sloped baffle. The condenser portion of the unit has a closed condenser coil comprising inner and outer coils. In operation, incoming liquid or mixed liquid and vapor refrigerant from the system being evacuated is fed into the evaporation portion, and the liquid refrigerant falls by gravity onto and around the coil. Vapor from the compressor outlet is fed to the coil where heat is transferred to the liquid refrigerant falling onto and surrounding the coil, and the condensed liquid is fed to the storage container. The heated liquid refrigerant surrounding the coil is thus evaporated and supplied to the compressor inlet. However, the combined evaporator, compressor and oil separator requires a relatively complicated construction.
It is an object of the present invention to overcome the problems and disadvantages associated with known refrigerant recovery system and to provide a system of the aforementioned type which is highly reliable, relatively simple in construction and operation, and inexpensive to manufacture and maintain.
It is yet another object of the present invention to provide a portable, electrically powered refrigerant recovery system which utilizes a single or unitary inlet/outlet manifold to provide a less costly manifold by incorporating several components such as ports, pressure relief valves, high and low pressure switches and gauges therein.
It is still a further object of the present invention to provide a less costly manifold which reduces constructional costs and time by incorporating a number of components such as ports and gauges therein.
Yet another object of the present invention is to provide a hot gas discharge port which, in combination with a check valve, permits the recovery system to be used as a vacuum discharge pump which can draw a vacuum on a system before being refilled with refrigerant.
Another object of the invention is to control the refrigerant recovery system in a manner which avoids short cycling of the compressor, which short cycling severely reduces compressor life.